As a radiation detector for detecting radiation, there conventionally exists a radiation detector configured as shown in FIG. 15. Such a radiation detector is provided with a scintillator 52 constituted by scintillator crystals C each having a rectangular parallelepiped shape arranged in a matrix. The scintillator crystal C is made of a material that converts radiation into fluorescence when radiation is incident. The fluorescence generated in the scintillator 52 is detected by a light detector 53 optically coupled to the scintillator 52 (see, for example, Patent Document 1).
FIG. 16 shows a structure of the scintillator 52. A reflection plate r that reflects fluorescence is arranged between adjacent scintillator crystals C. With this reflection plate r, adjacent scintillator crystals C are optically separated. The scintillator 52 is configured by assembling the scintillator crystals C and the reflection plates r as shown in FIG. 16.
The scintillator crystal C and the reflection plate r are integrated by a permeable material t that allows fluorescence to pass through. The permeable material t is formed by curing a liquid adhesive poured into the gap between the scintillator crystal C and the reflection plate r. With this permeable material t, the scintillator crystal C and the reflection plate r do not separate from each other. The permeable material t has a function of retaining the shape of the scintillator 52.
How the fluorescence generated by the conversion of the radiation in the scintillator crystal C advances inside the scintillator will be described. The asterisk in FIG. 16 shows a generation point of fluorescence located inside the scintillator crystal C. As shown in FIG. 16, a part of the fluorescence generated at the asterisk tries to exit from the side surface of the scintillator crystal C. Such fluorescence is hampered by the reflection plate r and never reaches the adjacent scintillator crystal C. As a result, the fluorescence eventually exits from the generation source scintillator crystal C to the light detector 53 side.
In other words, the position at which the fluorescence is incident to the light detector 53 is directly below the generation point of the fluorescence in the scintillator 52. Since the light detector 53 can determine the incident position of the fluorescence, the incident position of the fluorescence discriminated by the light detector 53 indicates the position of the generation point of the fluorescence in the scintillator 52.
If the reflection plate r is not provided between scintillator crystals C, the fluorescence generated in the scintillator crystal C spreads out over a wide range of the scintillator 52, resulting in difficulty of identifying the generation point of the fluorescence. The reflection plate r of the scintillator 52 plays an important role in identifying the generation point of the fluorescence.